Electrocatalysts are key for renewable energy technologies and other important industrial processes. Currently, noble metals and metal oxides are the most widely used catalysts for electrocatalysis. ...However, metal‐based catalysts often suffer from multiple disadvantages, including high cost, low selectivity, poor durability, impurity poisoning and fuel crossover effects, and detrimental effects on the environment. Therefore, carbon‐based metal‐free catalysts have received increasing interest as promising electrocatalysts for advanced energy conversion and storage. Recently, tremendous progress has been achieved in the development of low‐cost, efficient carbon‐based metal‐free catalysts for renewable energy technologies and beyond. Here, a concise, but comprehensive and critical, review of recent advances in the field of carbon‐based metal‐free catalysts is provided. A brief overview of various reactions involved in renewable energy conversion and storage, including the oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction, carbon dioxide reduction reaction, nitrogen reduction reaction, and bifunctional/multifunctional electrocatalysis, along with some challenges and opportunities, is presented.
The emerging carbon‐based metal‐free catalysts have been demonstrated to be promising alternatives to noble metal/metal oxide catalysts for various reactions, including the oxygen reduction reaction, the hydrogen evolution reaction, the oxygen evolution reaction, the carbon dioxide reduction reaction, and the nitrogen reduction reaction, and for bi/multifunctional electrocatalysis. A concise, but comprehensive and critical overview of this field, including preparation strategies, mechanisms, and applications, along with some challenges and perspectives, is presented.
Lithium‐ion capacitors (LICs) are a game‐changer for high‐performance electrochemical energy storage technologies. Despite the many recent reviews on the materials development for LICs, the design ...principles for the LICs configuration, the possible development roadmap from academy to industry has not been adequately discussed. Systematic understanding of device development is the foundation to more efficient utilization of advanced LICs materials. This review focuses on the principle of the recent configurations of LICs, the device design rationales, and new prelithiation techniques that are an integral part in LIC design. The authors also comment on the new generation multifunctional LICs that are capable of meeting the emerging applications in flexible electronics and other modern technologies. Finally, the status of LICs is presented and several key take‐home messages about minimizing the gaps between academic and industry requirements are proposed.
Lithium‐ion capacitors (LICs) are powerful competitors to supercapacitors and batteries due to their high energy‐power performance and long lifespan. The design rationale and device configuration of LICs are introduced, followed by the prelithiation methods and fabrication of multifunctional LICs. Finally, the status of commercial LICs and a possible roadmap of advanced LICs from laboratory to industry are discussed.
Lithium‐sulfur (Li‐S) batteries have attracted tremendous interest because of their high theoretical energy density and cost effectiveness. The target of Li‐S battery research is to produce batteries ...with a high useful energy density that at least outperforms state‐of‐the‐art lithium‐ion batteries. However, due to an intrinsic gap between fundamental research and practical applications, the outstanding electrochemical results obtained in most Li‐S battery studies indeed correspond to low useful energy densities and are not really suitable for practical requirements. The Li‐S battery is a complex device and its useful energy density is determined by a number of design parameters, most of which are often ignored, leading to the failure to meet commercial requirements. The purpose of this review is to discuss how to pave the way for reliable Li‐S batteries. First, the current research status of Li‐S batteries is briefly reviewed based on statistical information obtained from literature. This includes an analysis of how the various parameters influence the useful energy density and a summary of existing problems in the current Li‐S battery research. Possible solutions and some concerns regarding the construction of reliable Li‐S batteries are comprehensively discussed. Finally, insights are offered on the future directions and prospects in Li‐S battery field.
The research status of Li‐S batteries is briefly reviewed based on statistical analysis results. A summary of existing problems in the current Li‐S battery research is concluded with possible solutions and some concerns comprehensively discussed. Perspectives are proposed with respect to more reliable lithium‐sulfur batteries with rationally improved performance.
Multipartite entangled states are crucial for numerous applications in quantum information science. However, the generation and verification of multipartite entanglement on fully controllable and ...scalable quantum platforms remains an outstanding challenge. We report the deterministic generation of an 18-qubit Greenberger-Horne-Zeilinger (GHZ) state and multicomponent atomic Schrödinger cat states of up to 20 qubits on a quantum processor, which features 20 superconducting qubits, also referred to as artificial atoms, interconnected by a bus resonator. By engineering a one-axis twisting Hamiltonian, the system of qubits, once initialized, coherently evolves to multicomponent atomic Schrödinger cat states-that is, superpositions of atomic coherent states including the GHZ state-at specific time intervals as expected. Our approach on a solid-state platform should not only stimulate interest in exploring the fundamental physics of quantum many-body systems, but also enable the development of applications in practical quantum metrology and quantum information processing.
Their chemical stability, high specific surface area, and electric conductivity enable porous carbon materials to be the most commonly used electrode materials for electrochemical capacitors (also ...known as supercapacitors). To further increase the energy and power density, engineering of the pore structures with a higher electrochemical accessible surface area, faster ion‐transport path and a more‐robust interface with the electrolyte is widely investigated. Compared with traditional porous carbons, two‐dimensional (2D) porous carbon sheets with an interlinked hierarchical porous structure are a good candidate for supercapacitors due to their advantages in high aspect ratio for electrode packing and electron transport, hierarchical pore structures for ion transport, and short ion‐transport length. Recent progress on the synthesis of 2D porous carbons is reported here, along with the improved electrochemical behavior due to enhanced ion transport. Challenges for the controlled preparation of 2D porous carbons with desired properties are also discussed; these require precise tuning of the hierarchical structure and a clarification of the formation mechanisms.
Two‐dimensional (2D) porous carbon sheets, which can be synthesized by templating approaches, biomass carbonization, biomass carbonization–activation, in situ activation, etc, are good candidates for supercapacitors due to their advantages in their short ion‐transport length and high aspect ratio for electrode packing and electron transport.
Tackling the huge volume expansion of silicon (Si) anode desires a stable solid electrolyte interphase (SEI) to prohibit the interfacial side reactions. Here, a layered conductive polyaniline (LCP) ...coating is built on Si nanoparticles to achieve high areal capacity and long lifespan. The conformal LCP coating stores electrolyte in interlamination spaces and directs an in situ formation of LCP‐integrated hybrid SEI skin with uniform distribution of organic and inorganic components, enhancing the flexibility of the SEI to buffer the volume changes and maintaining homogeneous ion transport during cycling. As a result, the Si anode shows a remarkable cycling stability under high areal capacity (≈3 mAh cm−2) after 150 cycles and good rate performance of 942 mAh g−1 at 5 A g−1. This work demonstrates the great potential of regulating the SEI properties by a layered polymer‐directing SEI formation for the mechanical and electrochemical stabilization of Si anodes.
A layered conductive polyaniline (LCP) coating is built from a bottom‐up polymer design strategy for Si anodes. The in situ formation of LCP‐integrated solid electrolyte interphase (SEI) with uniform structure and flexible mechanical property enhances the stability of the electrode–electrolyte interface.
Carbon materials are usually used as the sulfur host in rechargeable lithium–sulfur (Li–S) batteries that are considered as promising electrochemical energy storage systems. However, the “shuttling” ...caused by the soluble lithium polysulfides (LiPSs) formed by the reaction of Li and sulfur causes rapid capacity fade and low sulfur utilization, greatly hindering their practical use. The carbon materials can also be tailored to prevent LiPS shuttling because of their abundant porosity and controllable surface chemical properties, which are divided into four specific functions: confining, trapping, blocking, and breaking up. Confinement means physically confining the LiPSs in pores in the carbon while trapping refers to chemical adsorption on the carbon surface to restrict their diffusion and promote their transformation to insoluble Li2S2/Li2S. Blocking means placing a barrier in the cells to inhibit LiPS diffusion to the anode, while breaking up means decreasing the size of the sulfur moiety to increase its affinity with carbons. The advantages and disadvantages of functional carbons in relation to these four functions are summarized and the specific ways to achieve them are highlighted. The design of advanced carbons with synergistic functions is discussed and some perspectives on the future development of carbons in Li–S batteries are given.
Functional carbon materials are widely used in lithium–sulfur batteries to remedy the shuttling of lithium polysulfides, which can be generalized into four different functions: confining, trapping, blocking, and breaking up. Research advances for the design of carbons with different roles and the corresponding performance improvement are discussed in detail. The perspectives on the challenges and solutions for future applications are proposed.
A simple and scalable method to fabricate graphene‐cellulose paper (GCP) membranes is reported; these membranes exhibit great advantages as freestanding and binder‐free electrodes for flexible ...supercapacitors. The GCP electrode consists of a unique three‐dimensional interwoven structure of graphene nanosheets and cellulose fibers and has excellent mechanical flexibility, good specific capacitance and power performance, and excellent cyclic stability. The electrical conductivity of the GCP membrane shows high stability with a decrease of only 6% after being bent 1000 times. This flexible GCP electrode has a high capacitance per geometric area of 81 mF cm−2, which is equivalent to a gravimetric capacitance of 120 F g−1 of graphene, and retains >99% capacitance over 5000 cycles. Several types of flexible GCP‐based polymer supercapacitors with various architectures are assembled to meet the power‐energy requirements of typical flexible or printable electronics. Under highly flexible conditions, the supercapacitors show a high capacitance per geometric area of 46 mF cm−2 for the complete devices. All the results demonstrate that polymer supercapacitors made using GCP membranes are versatile and may be used for flexible and portable micropower devices.
Graphene–cellulose paper (GCP) membrane materials fabricated by simple vacuum filtration are used as electrodes for flexible supercapacitors. The unique three‐dimensional interwoven structure of graphene nanosheets and cellulose fibers equips the GCP with excellent mechanical flexibility, high rate capability and capacitance per geometric area of 81 mF cm−2, and long cycling stability. GCP‐based flexible polymer supercapacitors with various architectures are demonstrated.
Au–Ni core‐shell nanorods (NRs) and Au–Pt–Ni core‐sandwich‐shell NRs are synthesized and exhibit high activity for selective H2O2 production via direct oxygen reduction. The epitaxial growth with ...coherent lattice fringes allow for the tuning of the oxygen reduction pathway. Moreover, a selectivity of 95% and mass activity of 192.9 A g−1noble metal are achieved using Au–Pt–Ni NRs at 150 mV overpotential.
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